The internal combustion engine conventionally includes an air induction system (AIS) for delivering ambient air to the throttle body and ultimately into the combustion chamber as part of an air-fuel mixture. The air induction system includes an air duct that initially takes in the ambient air and passes the incoming air into and through the air filter box. Typically the air duct is a generally inexpensive unit that is conventionally positioned adjacent more expensive under hood components such as the Air Conditioner (A/C) condenser, the radiator and parts associated with the radiator including the fan unit (or units) and the fan shroud.
During an impact event, the radiator and the associated fan unit and shroud are pushed vehicle rearward into the engine compartment. This problem can arise even in a low speed impact in which components of the “cooling pack” (the A/C condenser, the radiator, the fan unit, and the fan shroud) as well as the bolster are pushed vehicle-rearward by about 100 mm. To minimize the additional damage to the radiator, the fan unit and the fan shroud, industry requirements for “Low Speed Damageability” (LSD) exist for automotive vehicles and are applied to the AIS ducts. These rules require that the zone vehicle-rearward of the radiator be either empty or only contain parts that will exert minimal resistance on the movement of the radiator, fan unit and fan shroud in an impact event. The force from the AIS duct that resists movement of the radiator, fan unit and fan shroud must be sufficiently low so that the A/C condenser, radiator, fan unit and fan shroud are not damaged during an impact event, to minimize the cost of repair.
Given the concern over a possible impact event, today's AIS dirty side duct (DSD) is at risk of not meeting the safety LSD cascaded target. The cascaded target sought after by automotive designers involved in vehicle safety is to have the DSD collapse when put under a predetermined acceptable force such as 500N in an impact event in order to meet LSD requirements. A “successful” impact event result is that there is no post-crash damage to components such as the NC condenser, the radiator, the fan unit, the fan shroud, the battery or the battery cover.
Of components at risk during an impact event, the air induction duct is usually the most inexpensive component to sacrifice and replace. In an effort to respond to LSD requirements, auto manufacturers desire to provide an air duct that is strong enough to perform under all engine conditions but yet is weak enough to break in a low speed impact and vacate space for more complex and more expensive components to move into without causing damage to these components. In an effort to satisfy this need, manufacturers use soft elastomer/rubber materials for the AIS ducts and hoses. However, elastomeric parts can cost and weigh more than that of molded rigid plastic parts. Such components also tend to be heavier than molded rigid plastic parts and thus add undesirable extra weight to the vehicle.
Accordingly, known approaches to reducing damage to expensive under hood components in an impact event have not always produced satisfactory results. As in so many areas of vehicle technology, there is always opportunity for improvement related to designs for AIS components.